Increasing environmental legislations on pollutant emissions originated from fossil fuel combustion and intention of increasing the life of existing fossil fuels give rise to the use of renewable sources. Biomass at this juncture, with its renewable nature and lower pollutant emission levels becomes an attractive energy resource. However, only seasonal availability of biomass and operation problems caused by high alkaline content of biomass ash restrict its combustion alone. These problems can be overcome by co-combustion of biomass with lignite. With its high fuel flexibility and high combustion efficiency, fluidized bed combustion is the most promising technology for co-firing. To improve and optimize the operation of co-firing systems a detailed understanding of co-combustion of coal and biomass is necessary, which can be achieved both with experiments and modeling studies. For this purpose, a comprehensive system model of fluidized bed combustor, previously developed and tested for prediction of combustion behaviour of fluidized bed combustors fired with lignite was extended to co-firing lignite with biomass by incorporating volatile release, char combustion and population balance for biomass. The model predictions were validated against experimental measurements taken on METU 0.3 MWt AFBC fired with lignite only, lignite with limestone addition and about 50/50 lignite/olive residue mixture with limestone addition. Predicted and measured temperatures and concentrations of gaseous species along the combustor were found to be in good agreement. Introduction of biomass to lignite was found to decrease SO2 emissions but did not affect NO emissions significantly.

Fluidized bed is a suitable technology for combustion and gasification of biomass materials. Hydrodynamics occurring in the bed is crucial for the design and operation of the combustion or gasification unit. In the present study, hydrodynamic behavior of binary mixtures of biomass-silica sand in a bubbling fluidized bed was experimentally investigated. Five different biomass materials and silica sand with three different particle sizes were employed to form binary mixtures. Biomass materials were rice husk, sawdust, wheat straw, hazelnut shell and olive cake which are all potential energy sources for Turkey. Effects of mass percentage of biomass and particle size of silica sand on minimum fluidization velocity of the mixtures were determined. Comparisons between results of the present study and predictions of available correlations proposed for minimum fluidization velocity of binary mixtures were carried out. Mixing and segregation characteristics of biomass-silica sand binary mixtures were investigated for mixtures having different mass fraction of biomass and different silica sand particle sizes. Fluidization and bubbling behaviors of mentioned mixtures were observed in a 2-D fluidized bed and images taken during steady-state operation of bed were presented as visual tools to guide fluidization characteristics of the bed. Mass percentage increase of rice husk, wheat straw and sawdust resulted in increase in minimum fluidization velocity of the mixture whereas change in mass fraction of olive cake and hazelnut shell had no effect on minimum fluidization velocity. Minimum fluidization velocity increased with increase of silica sand particle size for all biomass-silica sand mixtures having same mass percentage of biomass. Vertical mixing pattern in the bed at steady state conditions were found almost same for all biomass-silica sand mixtures. Biomass acted as flotsam and accumulated mostly at the top of the bed and silica sand acted as jetsam and accumulated mostly at the bottom of the bed. 2-D bed experiments showed that mixing biomass materials with silica sand provides desired bubbling behavior in the bed.

This dissertation describes the use of measured aerosol size distributions and size-resolved hygroscopic growth to examine the physical and chemical properties of several particle classes. The primary objective of this work was to investigate the optical and cloud forming properties of a range of ambient aerosol types measured in a number of different locations. The tool used for most of these analyses is a differential mobility analyzer / tandem differential mobility analyzer (DMA / TDMA) system developed in our research group. To collect the data described in two of the chapters of this dissertation, an aircraft-based version of the DMA / TDMA was deployed to Japan and California. The data described in two other chapters were conveniently collected during a period when the aerosol of interest came to us. The unique aspect of this analysis is the use of these data to isolate the size distributions of distinct aerosol types in order to quantify their optical and cloud forming properties. I used collected data during the Asian Aerosol Characterization Experiment (ACE-Asia) to examine the composition and homogeneity of a complex aerosol generated in the deserts and urban regions of China and other Asian countries. An aircraft-based TDMA was used for the first time during this campaign to examine the size-resolved hygroscopic properties of the aerosol. The Asian Dust Above Monterey (ADAM-2003) study was designed both to evaluate the degree to which models can predict the long-range transport of Asian dust, and to examine the physical and optical properties of that aged dust upon reaching the California coast. Aerosol size distributions and hygroscopic growth were measured in College Station, Texas to investigate the cloud nucleating and optical properties of a biomass burning aerosol generated from fires on the Yucatan Peninsula. Measured aerosol size distributions and size-resolved hygroscopicity and volatility were used to infer critical supersaturation distributions of the distinct particle types that were observed during this period. The predicted cloud condensation nuclei concentrations were used in a cloud model to determine the impact of the different aerosol types on the expected cloud droplet concentration. RH-dependent aerosol extinction coefficients were also calculated.

Biomass conversion into forms of energy is receiving current attention because of environmental, energy and agricultural concerns. The purpose of this thesis is to analyze the environmental, energy, economic, and technological aspects of using a form of biomass, switchgrass (panicum virgatum), as a partial or complete replacement for coal in power generation and cogeneration systems. To examine the effects of such a substitution, an environmental biocomplexity approach is used, wherein the agricultural, technological, economic, and environmental factors are addressed. In particular, lifecycle analysis (LCA) and a three-dimensional integrated economic, energy and environmental analysis is employed. The effectiveness of alternate technologies for switchgrass preparation, harvest and use in terms of greenhouse gas impact, cost and environmental implications is examined. Also, different scenarios of cofiring and biomass preparation pathways are investigated. Optimization of the total biomass power generation cost with minimum greenhouse gas effect is undertaken using mathematical programming for various alternate competitive biomass processing pathways. As a byproduct of this work a generic tool to optimize the cost and greenhouse gas emissions for allocation of fuel sources to the power generating sinks is developed. Further, this work discusses the sensitivity of the findings to varied cofiring ratios, coal prices, hauling distances, per acre yields, etc. Besides electricity generation in power plants, another viable alternative for reducing greenhouse gases (GHGs) is the utilization of biomass in conjunction with combined heat and power (CHP) in the process industries. This work addresses the utilization of biowaste or biomass source in a processing facility for CHP. A systematic algebraic procedure for targeting cogeneration potential ahead of detailed power generation network design is presented. The approach presented here effectively utilizes the biomass and biowaste sources as external fuel, and matches it with the use and dispatch of fuel sources within the process, heating and non-heating steam demands, and power generation. The concept of extractable energy coupled with flow balance via cascade diagram has been used as a basis to construct this approach. The work also discusses important economic factors and environmental policies required for the cost-effective utilization of biomass for electricity generation and CHP.

In this work, 80% lime-treated rice straw and 20% lime-treated chicken manure were used as substrates in rotary fermentors. Countercurrent fermentation was performed at various volatile solid loading rates (VSLR) and liquid residence times (LRT). The highest acid productivity of 1.69 g/(L·d) was at a total acid concentration of 32.4 g/L. The highest conversion and yield were 0.692 g VS digested/g VS fed and 0.29 g total acids/g VS fed, respectively. The continuum particle distribution model (CPDM) was used to predict product concentrations at various VSLR and LRT. CPDM predicted the experimental total acid concentration and conversion at an average error of 6.41% and 6.55%, respectively. A fixed-bed fermentation system was designed to perform pretreatment and fermentation in the same unit. High product concentrations (~48 g/L) as well as high conversions (0.741 g VS digested/g VS fed, F4, Train B) were obtained from the same fermentor. CPDM was extended to predict product concentrations in the fixed-bed fermentation system. The model gave a good estimate of the product concentrations and retention time. After biomass fermentation, the residue can be combusted to generate heat. For pretreatment purposes, the use of ash can replace lime. A study was performed using ash as a potential pretreatment agent. Ash from raw poplar wood was effective in pretreating poplar wood; however, ash from bagasse fermentation residues was not useful in pretreating bagasse. Previous modeling studies indicate that a conversion of 95% could be achieved with bagasse using countercurrent fermentation. Because lignin constitutes 13% of the dry weight of bagasse, this means lignin would have to be digested to obtain a conversion of 95%. Experiments on the fermentation of enzymatically liberated lignin from both poplar wood and bagasse do not show that solubilized lignin was fermented to organic acids by using a mixed culture of marine microorganisms. Two buffer systems (ammonium bicarbonate and calcium carbonate) were used to compare product concentrations of carboxylic acid fermentations using office paper and chicken manure. It has been demonstrated that the total product concentration using ammonium bicarbonate is almost double the product concentration using calcium carbonate.

A proprietary technology owned by Texas A

Commercial activated carbon and newly polymer-derived carbon were utilized to selectively remove the model fermentation inhibitor, furfural, from water solution during bio-ethanol production. Morphology, pore structure and surface chemistry of the sorbents were characterized. The oxygen groups on the carbon surface were believed to have contributed to the decrease on the selectivity of activated carbon between furfural and sugars (Sugars are the valuable source of bio-ethanol production and should not be separated from solution). Oxidization of activated carbon by nitric acid generated more information which supports the above assumption. Different adsorption isotherm models and kinetic models were studied to fit commercial activated carbon and polymer-derived carbon individually. Bacterial cell growth, sugar consumption, and ethanol yield during the fermentation were investigated after inhibitors were selectively removed from the broth. The fermentation time was reduced from one week to one day after inhibitor removal. Different methods of sorbent regeneration were investigated, including thermal regeneration, pH adjustment and organic solvent stripping. Low ethanol-containing water solution appears to be the most cost-effective way to regenerate the spent sorbent in the industrial application. A sorption/desorption cycle was designed and the sorbents were regenerated in a fixed-bed column system using ethanol-containing liquid from fermentation. The results were stable after running 20 times of sorption/desorption cycle.

This work makes an attempt to explain the origin, features and potential applications of the elevation bias of the synthetic aperture radar interferometry (InSAR) datasets over areas covered by vegetation. The rapid development of radar-based remote sensing methods, such as synthetic aperture radar (SAR) and InSAR, has provided an alternative to the photogrammetry and LiDAR for determining the third dimension of topographic surfaces. The InSAR method has proved to be so effective and productive that it allowed, within eleven days of the space shuttle mission, for acquisition of data to develop a three-dimensional model of almost the entire land surface of our planet. This mission is known as the Shuttle Radar Topography Mission (SRTM). Scientists across the geosciences were able to access the great benefits of uniformity, high resolution and the most precise digital elevation model (DEM) of the Earth like never before for their a wide variety of scientific and practical inquiries. Unfortunately, InSAR elevations misrepresent the surface of the Earth in places where there is substantial vegetation cover. This is a systematic error of unknown, yet limited (by the vertical extension of vegetation) magnitude. Up to now, only a limited number of attempts to model this error source have been made. However, none offer a robust remedy, but rather partial or case-based solutions. More work in this area of research is needed as the number of airborne and space-based InSAR elevation models has been steadily increasing over the last few years, despite strong competition from LiDAR and optical methods. From another perspective, however, this elevation bias, termed here as the “biomass impenetrability”, creates a great opportunity to learn about the biomass. This may be achieved due to the fact that the impenetrability can be considered a collective response to a few factors originating in 3D space that encompass the outermost boundaries of vegetation. The biomass, presence in InSAR datasets or simply the biomass impenetrability, is the focus of this research. The report, presented in a sequence of sections, gradually introduces terminology, physical and mathematical fundamentals commonly used in describing the propagation of electromagnetic waves, including the Maxwell equations. The synthetic aperture radar (SAR) and InSAR as active remote sensing methods are summarised. In subsequent steps, the major InSAR data sources and data acquisition systems, past and present, are outlined. Various examples of the InSAR datasets, including the SRTM C- and X-band elevation products and INTERMAP Inc. IFSAR digital terrain/surface models (DTM/DSM), representing diverse test sites in the world are used to demonstrate the presence and/or magnitude of the biomass impenetrability in the context of different types of vegetation – usually forest. Also, results of investigations carried out by selected researchers on the elevation bias in InSAR datasets and their attempts at mathematical modelling are reviewed. In recent years, a few researchers have suggested that the magnitude of the biomass impenetrability is linked to gaps in the vegetation cover. Based on these hints, a mathematical model of the tree and the forest has been developed. Three types of gaps were identified; gaps in the landscape-scale forest areas (Type 1), e.g. forest fire scares and logging areas; a gap between three trees forming a triangle (Type 2), e.g. depending on the shape of tree crowns; and gaps within a tree itself (Type 3). Experiments have demonstrated that Type 1 gaps follow the power-law density distribution function. One of the most useful features of the power-law distributed phenomena is their scale-independent property. This property was also used to model Type 3 gaps (within the tree crown) by assuming that these gaps follow the same distribution as the Type 1 gaps. A hypothesis was formulated regarding the penetration depth of the radar waves within the canopy. It claims that the depth of penetration is simply related to the quantisation level of the radar backscattered signal. A higher level of bits per pixels allows for capturing weaker signals arriving from the lower levels of the tree crown. Assuming certain generic and simplified shapes of tree crowns including cone, paraboloid, sphere and spherical cap, it was possible to model analytically Type 2 gaps. The Monte Carlo simulation method was used to investigate relationships between the impenetrability and various configurations of a modelled forest. One of the most important findings is that impenetrability is largely explainable by the gaps between trees. A much less important role is played by the penetrability into the crown cover. Another important finding is that the impenetrability strongly correlates with the vegetation density. Using this feature, a method for vegetation density mapping called the mean maximum impenetrability (MMI) method is proposed. Unlike the traditional methods of forest inventories, the MMI method allows for a much more realistic inventory of vegetation cover, because it is able to capture an in situ or current situation on the ground, but not for areas that are nominally classified as a “forest-to-be”. The MMI method also allows for the mapping of landscape variation in the forest or vegetation density, which is a novel and exciting feature of the new 3D remote sensing (3DRS) technique. Besides the inventory-type applications, the MMI method can be used as a forest change detection method. For maximum effectiveness of the MMI method, an object-based change detection approach is preferred. A minimum requirement for the MMI method is a time-lapsed reference dataset in the form, for example, of an existing forest map of the area of interest, or a vegetation density map prepared using InSAR datasets. Preliminary tests aimed at finding a degree of correlation between the impenetrability and other types of passive and active remote sensing data sources, including TerraSAR-X, NDVI and PALSAR, proved that the method most sensitive to vegetation density was the Japanese PALSAR - L-band SAR system. Unfortunately, PALSAR backscattered signals become very noisy for impenetrability below 15 m. This means that PALSAR has severe limitations for low loadings of the biomass per unit area. The proposed applications of the InSAR data will remain indispensable wherever cloud cover obscures the sky in a persistent manner, which makes suitable optical data acquisition extremely time-consuming or nearly impossible. A limitation of the MMI method is due to the fact that the impenetrability is calculated using a reference DTM, which must be available beforehand. In many countries around the world, appropriate quality DTMs are still unavailable. A possible solution to this obstacle is to use a DEM that was derived using P-band InSAR elevations or LiDAR. It must be noted, however, that in many cases, two InSAR datasets separated by time of the same area are sufficient for forest change detection or similar applications.

Univ., Diss.--Utrecht, 2007.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on December 30, 2009). Thesis advisor: Dr. Jinglu Tan. Includes bibliographical references.